During the third year of the project the system for detecting and analyzing mitotic (somatic) chromosomal aberrations will be used to screen a large number of chemicals and drugs. The drugs will include experimental cancer chemotherapy compounds supplied by investigators at the Sloan-Kettering Institute. The tests should establish reliability of the Aspergillus nidulans test system. Specifically the following types of genetic damage will be sought in a single treatment with a potential mutagen: (a) mitotic nondisjunction leading to aneuploidy, (b) mitotic recombination, and (c) recessive mutations. Any drug which is found to cause segregation of genetic variants will be a candidate for more thorough analysis. This should allow the categorization of a drug as a mutagen, recombinogen, a clastogen, or other. Concurrently, the determination of the optimum conditions for meiotic analysis will be completed. The major impediment which still remains is the most meaningful approach to quantitation of events. It is hoped that methods can be devised to establish rates of genetic damage rather than frequency. This same impediment must be overcome in the detection of translocation in germinating conidia.